Re: Eletronic ingintion VS. Points which is better?
Points work well when they're just installed and set properly. But as they wear, the point material migrates from one side to the other, (very slight DC arc welding going on every time the points open), leaving a crater on 1 side and a peak on the other. That changes the gap, plus the phenolic insulator riding on the cam slowly wears, changing the dwell.
You get the idea.
Electronic ignitions use a non contact device, commonly a magnetic sensor, to initiate the spark. There's no wear so it doesn't change with time. If EFI is used, the ECU can control the advance to suit different conditions, resulting in better efficiency.
I expect people here have been a bit reluctant to answer your questions as you sound unsure of what you're doing, "..resistors and diodes or something like that..".
Try to find someone local to you who is familiar with the electrics on a boat to help you. Safety is involved with this kind of project.
I'm familiar with older OMC's, not Cobras, but follow your shift cable to the engine; does it go to a plate with a small switch on it? That may be the interrupter. Press it while running, the engine should slow.